Method for destruction of weeds



been unsuccessful.

United States Patent O This invention relates to methods for killing or preventing weeds, or undesirable plant growth, and to compositions employed in practicing such methods.

It is already known to use trisubstituted urea derivatives as herbicides (US. patent specification No. 2,655,445). It is also already known that cyclohexyl derivatives of urea of the general formula:

. R A (C1195 CHNCO-N R!!! RI! in which R, R" and R' represent hydrogen, an alkyl group containing 1 to 8 C atoms, or an alkenyl group, have herbicidal activity (US. patent specification No. 2,661,272). This activity is unsatisfactory both as a total herbicide and as a preemergence herbicide. Attempts to improve the inadequate activity of these substances by varying the radicals R, R" and R have Even the replacement of the cycloheXyl radical hitherto exclusively described by cycloaliphatic radicals with a smaller number of carbon atoms, for example by a cyclo-pentyl radical, has given no improvement but in most cases a considerable diminution in the herbicidal activity.

, We have now found, surprisingly,- that compounds having an economically exploitable herbicidal activity are obtained by replacing the cyclohexyl radical in the said urea derivatives by the cycloheptyl or cyclo-octyl radical. The following table illustrates the variation in the total herbicidal action when the cyclohexyl radical is replaced by the cyclopentyl, cycloheptyl and cyclo-octyl radicals. The figures given relate to the total herbicidal action of the said substances with an amount of active substance in which n has the value 6 or 7, R, R and R represent hydrogen or an alkyl, alkenyl or aryl group and Rv and R may also be part of a common ring, have hitherto not been described. They may be prepared by methods which are known per se. 7

Thus by reacting cycloheptylamine or cyclo-octylamine of the Formula II in which n is equal to 6 or 7 with phosgene, the corresponding isocyanates ofthe Formula III (n=6 or 7) are obtained which in turn react with primary or secondary amines with the formation of the urea derivatives of the Formula I:

\ 3,001,861 Patented Sept. 26, 1961 Suitable initial materials for the reaction are the hydrochlorides of cycloheptylamine and cyclo-octylamine which may be reacted in an inert solvent, such as dry benzene, toluene, xylene, dioxane, cyclohexane, phenol ethers, ethyl acetate and the like, with phosgene, preferably at temperatures above 50 C. The reaction of the cycloheptyl and cyclo-octyl isocyanates with primary or secondary amines, as for example, methyl-, ethyl-, butyl-, dimethyl-, diethyl-, methylbutyl-, dicycloheXyl-amine, methylaniline, pyrrolidine, piperidine or morpholine, may also occur in the same solvents, temperatures between 0 and C. usually being suflicient. The working ,up is dependent on the kind of substituted urea and the choice of solvent.

' The compounds of the general Formula I are insoluble in water; they are mainly obtained in crystalline form and can be purified by recrystallization; in so far as they are obtained in the form of oils they can be distilled in vacuo.

r The procedure may however, also be that carbarnic acid chlorides of the Formula IV are prepared from secondary amines with phosgene and these are reacted with cycloheptylamines or cyclo-octylamines of the Formula V in which n is equal to 6 or 7:

tives of the general Formula I thus occurring in crystalline form or as extractable oils.

Compounds of the general Formula I can also be obtained by consecutively replacing the two NH -groups of urea by substituted amines according to the following Reaction (a) takes place in aqueous hydrochloric acid solution at temperatures above 75 C. The monosubstituted urea of the Formula VI (in which n=6 or 7) can readily be separated by filtration by suction from the ammonium chloride dissolved in water. The reaction (b) requires temperatures above 150 C. and may be.- carried out in high boiling point solvents, such as nitrobeuzene, dichlorbenzene, phenol ethers. The more highly substituted urea derivatives of the Formula I are more readily soluble in these solvents than the monosubstituted ureas of the Formula VI and can therefore be separated therefrom.

The parts specified in the following prescriptions are parts by weight.

PRESCRIPTION A Dry halogen chloride is led into a solution of 127 parts of cyclo-octylamine in 410 parts of dry dioxane at room temperature until the whole of the amine has been converted into the hydrochloride. 'Ihen dry phosgene isled into the solution kept at 90 C. until the color of the solution has changed to yellow-brown, which requires about 2m 3 hours. After distilling 01f about 100 parts of dioxane (whereby the excess of phosgene and hydrogen chloride are removed), dimethylamine is led into the solution of the cyclo-octyl isocyanate formed at room temperature until itis saturated and the reaction mixture kept -at 50 C. for 1 hour after the end of the introduction; it is t-hen'allowed to cool and the precipitated l-cyclooctyl-3.3-dimethylurea is filtered otf by suction-suspended in water and after repeated filtration by suction dried in a vacuum drying cabinet at 60 C. If necessary the compound can be recrystallized from cyclohexane. 168 parts of 1-cyclo-octyl-3.S-dimethylurea of the melting point 137 to-137.5 C. are obtained.

From 54 parts of cycloheptylamine in 550 parts of dry dioxane there are obtained by the same process 56 parts of 1-cycloheptyl-3.3-dimethylurea which has a melting point of 152 to 153 C. when recrystallizedfrom dilute alcohol.

PRESCRIPTION B temperature-is kept below 40 C. by cooling. After the end of the addition of the solution, the reaction mixture is heated up to 90 C., the introduction of phosgene ended andthe reaction mixture kept at 90 C. until no further hydrogen chloride is disengaged. After distilling 01f the solvent, 169 parts of cyclo-octyl isocyanate pass over as a colorless'liquid at 105 C.-under 21 mm./Hg pressure.

26 parts of dicyclohexylamine dissolved in 25; parts of dry dioxane are dripped at room temperature" into asolution of 20 parts of cyclo-octyl isocyanate and 100 parts of dioxane. After the end of the addition, the reaction .rniXture-is .keptfor /2 to 1 hour at 50 C. and then allowed to. cool andpoured into water. After filtration by suction and drying, 42 parts of l-cyclo-octyl-3l3-dicyclohexylurea are obtained, which melts at 156 to 157 C.

By the same process there are obtained from20 parts of cycIo-octyl isocyanate and 20 parts of N-ethyl-orthotoluidine: .21 parts of 1-cyclo-octyl-3-ethyl-ortho-toluylurea whichmelts at 162 to 163 C. when recrystallized from alcohol;

From 20 parts of cyclo-octyl isocyanate and 20 parts of cyclo-oetylamine: 20 parts of 1-cyclo-octyl-3-cyclooctyl-urea which melts at 185 to 186 C.;

From 20 parts of cyclo-octyl isocyanate by passing in gaseous methylamine until it is saturated: 22 parts of 1-cyclo-octyl-3-methylurea of the melting point 132 to 133 C.;

From 20 parts of cyclo-octyl isocyanate and 13 parts of V morpholine: 28 parts of N-cyclo-octyl-carbamic acid fromdilute alcohol. :the meltingpoint 179to 180 C. are obtained.

due recrystallized from cyclohexane. cyclo-octyl3.3-dimethylurca of the meltingpoint 136 morpholide which has a melting point of 158 to 159 C. when recrystallized from benzene and cyclohexane in the ratio 1:1

From 20 parts of cyclo-octyl isocyanate and 13 parts of piperidine: 26 parts of N-cyclo-octyLNCNGpentamethylureawhich melts at 138 to 139 Cqwhen recrystallizedfrom cyclohexane; and

.From20 parts;of.cyclo+octy1 isocyanate and 8; parts of pyrrolidine: 19 parts of. N-cyclo-octyl-N'.N-tetramethylurea which has a meltingpoint of to 151 C.\Wh6n recrystallized from .cyclohexane.

PRESCRIPTION C 20 parts of cyclo-octyl isocyanate are reacted with 20 parts of diethylamine in the way described in Prescription B. After pouring the reaction mixture into water and acidifying with dilute hydrochloric acid, the oily layer formed is extracted with ether, .dried with sodium sulfate and subjected to vacuum distillation. 24 parts of '1-cyclo-octyl-3,3-diethylurea are obtained which boils at 150 C. under a pressure of 0.2 mm./Hg. The compound becomes solid upon standing and melts at 68 C.

By the same process there are obtained:

From 20 parts of cyclo-octyl isocyanate and 34 parts of dibutylamine: 22 parts of 1-cyclo-octyl-3.3-dibuty1- urea which boils at 162 to 163 C. under a pressure of 0.4 mm./Hg and melts at 67 C.;

From 20 parts of cyclo-octyl isocyanate and 16 parts of methylaniline: 18 parts of l-cyclo-octyl-3-methyl-3- phenylurea with the boiling point 149 C. at a pressure of 0.05 rum/Hg; and from 20 parts of cyclo-octyl isocyanate and 15 parts of ethylbutylamine: 13 parts of 1 cyclo-octyl-3-ethyl-3 butyl-urea which boils at 144 C. under a pressure of 0.1 mm./Hg.

PRESCRIPTION D iheated for '5 hours at 100 C. It is allowed to cool,

filtered bysuction, washed-with Water and recrystallized 113 parts of l-cyclo-octylureaof 113 parts of l-cyclo-octylurea are suspended in 400 leading in dimethylamine, it is then heated to refluxing :temperature and the reaction mixture kept for another 5 hours'at a temperature of to C.

The solvent is evaporated in vacuo and the solid resi- 70 parts of 1- to 137 C. are obtainedrit is identical withtheproduct described in Prescription A.

PRESCRIPTION E 53 parts of dimethylcarbamicacid chloride are dis- .solved in 250 parts of dry chloroform and 100 parts of dry pyridine are added thereto; 50 parts of cyclo-octyloctyl-3.3-dimethylurea of the melting point 136 to.137

C. are obtained which is identical with the product described in Prescription A.

The activity ofthe herbicides according to this invention is illustrated by the following examples:

Example 1 1-cyclo-octyl-3.3-dirnethylurea is used in the greenhouse in.-.am0unts.of.2.5, 5:and..10..kilograms;per hectare in 1,200 litres of water with the following plants: -Sinapis alba, Avenaasativa, Poa annua, Galium aparine, Galinsoga parviflora and Polygonum persicaria. The beginning of the toxic action of the agent can be observed at the tips of the leaves of the plants even after 1 or 2 days. After about 10 days the plants are practically completely withered.

Example 2 A row of oats and a row of mustard are sown in sandy earth in each of two clay dishes of an area 25 x 30 centimetres. An aqueous solution of cyclo-octyldimethylureaprepared with the addition of a dispersing agent is sprayed onto the earth in such amounts that they correspond in one clay dish to 2 kilograms and in the other clay dish to kilograms of active substance per hectare. At first the oats and mustard seedlings develop normally. After 5 to 7 days, chlorotic phenomena occur especially at the leaf tips, and after 2 or 3 Weeks the young plants are completely destroyed. A fresh sowing with oats and mustard seed is carried out after a further 3 weeks in I the same earth which has been treated 6 weeks previously with cyclo-octyldimethylurea. The new plantlets are also completely withered 2 to 3 weeks after sprouting.

Example 3 An agricultural working area which is strongly infested with the Weeds; Galinsoga parviflora, Raphanus raphanistram, Sinapis arvensis, Atriplex patulum, Stellaria media, Chamomilla matricaria, Polygonam persicarla, and Panicam sanguinale, is sprayed with cyclooctyldimethylurea in an amount of 15 kilograms per hectare in 1,000 litres of water. The weeds are completely destroyed after 3 to 4 weeks. A new sowing of oats and mustard seed after about 4 months shoots completely and grows normally.

Example 4 On waste land, perennial grasses, dandelion, yarrow, plantain and clover are sprayed, for purposes of comparison, with 1-cyclo-octyl-3.3-dimethylurea, l-cyclo-heptyl- 3.3-dimethy1urea, 1-cycloheXyl-3.S-dimethylurea and 1- cyclopentyl-3.3-dimethylurea, in each case in an amount of 15 kilograms per hectare in 1,200 litres of water. After 5 weeks the following percentages are determined for the weed-killing action of the urea derivatives used:

Percent Cyclo-octyl-dirnethylurea 100 Cycloheptyl-dimethylurea to Cyclohexyl-dimethylurea 55 to 60 Cyclopentyl-dimethylurea 15 to 20 Example 5 Carrot and beetroot seeds are sown in an agricultural working area. On the same day cyclo-octyldimethylurea, cyclohexyldimethylurea and para-chlorphenyldimethylurea are sprayed on the same area in amounts of 1 kilogram per hectare in 1,000 litres of water. 3 weeks after the sprouting of the cultivated plants, the following comparative appraisement results on an average:

Sproutage of cultivated Sproutage Substance used plants in percent of weeds in percent cyelo-octyl-dirnethylurea (slight growth in- 5 to 15.

hibition). cyclohexyl-dimethylnrca d 60 to 65. parachlorphenyl-dlmethylurea.- 45 to 50 0 to 5.

The weeds which sprout in the control areas are Atriplex patulum, Chamomilla matricaria, Stellaria media, Capsella bursa pastoris, Spergula arvensis, Senecio vulgaris', Sinapis arvensis, Galinsoga parviflora, Polygonum avicalare, Polygonam persicaria and annuals, as for exwhere n is one of the integers 6 and 7 and R and R" are selected from the group consisting of hydrogen and alkyl having from 1 to 2 carbon atoms.

2. A method as claimed in claim 1 wherein said urea derivative is 1-cyclo-octyl-3.3-dimethyl urea.

3. A method as claimed in claim 1 wherein the urea derivative is l-cycloheptyl-S .3-dimethyl urea.

References Cited in the file of this patent UNITED STATES PATENTS Searle Dec. 1, 1953 Bortnick Dec. 24, 1957 

1. A METHOD FOR THE DESTRUCTION AND PREVENTION OF WEEDS WHICH COMPRISES APPLYING TO A LOCUS TO BE PROTECTED, IN AN AMOUNT SUFFICIENT TO EXERT A HERBICIDAL ACTION, A UREA DERIVATIVE REPRESENTED BY THE FORMULA 